Silverado bogs out and backfires when first started

[scoof84]

I have a 2000 Silverado z71 5.3l my problem is intermittent bogging/backfiring after startup. The truck starts fine every time but it is when you put it in gear and hit the gas it stumbles and backfires through the intake for the first minute or so. If I baby the throttle it will eventually clear up and run fine after about a mile. It does this cold most of the time but often does it warm also. Fuel pressure is good it has been tuned up I cant find any intake leaks. After it clears up it seems to run fine but it is really irritating when I go to pull out of a gas station in traffic and I have to pull over and wait 30 to 60 seconds of idle then it runs normal. anybody else have this issue?

[brian_k24]

It sounds like what my 2003 Siverado 5.3 did a few years back. it would run rough, hesitate, and stumble until it warmed up some. I was not getting any check engine lights but when I checked with my scan tool it showed LTFT (long term fuel trim) was very high. I replaced the intake manifold gaskets and solved the problem. You could see that the old gaskets had failed as soon as I pulled the manifold.